# Photonic Terahertz for 6G Communication

## TL;DR

This paper reviews recent advances in photonic terahertz (THz) communication for 6G, highlighting its potential for high-speed applications like holographic communication.

## Contribution

The paper provides a comprehensive review of photonic THz communication technologies, focusing on device, system, and antenna innovations.

## Key findings

- Photonic methods offer advantages in ultra-wideband signal generation and fiber-optic integration over conventional THz systems.
- Multi-parameter optimization improves bandwidth efficiency in single-row carrier photodiodes.
- High spectral efficiency and MIMO transmission mechanisms are advancing THz system performance.

## Abstract

Terahertz (THz) communication has become a key enabling technology for the future sixth generation (6G) due to its rich spectrum resources, supporting emerging applications such as holographic communication and ultra-wideband transmission. This article provides a comprehensive review of recent advances in photonic THz communications, covering device, system, and antenna technologies. First, the electronic bottlenecks in conventional THz systems, including limited bandwidth and severe phase noise generated by frequency doubling, are discussed, emphasizing the advantages of photonic methods in ultra-wideband signal generation and seamless integration with fiber-optic networks. Then, the effects of the carrier transit time, absorber layer thickness, and saturation effects on the bandwidth efficiency performance in single-row carrier photodiodes are reviewed, as well as multi-parameter co-optimization strategies for an enhanced performance. In addition, the latest progress in high spectral efficiency (SE) multi-dimensional multiplexing, lightweight high-gain lens antennas and multi-antenna MIMO transmission mechanisms in multi-antenna THz systems are also summarized. Finally, the prospects and challenges of photonic THz communications in long-distance links and space applications are discussed.